[openwrt/openwrt] px5g-mbedtls: Fix permission of private key

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/929c9a58c9a17a3ca8d2a3be0c5dc4ac98e848e2

commit 929c9a58c9a17a3ca8d2a3be0c5dc4ac98e848e2
Author: Hauke Mehrtens <hauke at hauke-m.de>
AuthorDate: Sun Nov 5 23:05:24 2023 +0100

    px5g-mbedtls: Fix permission of private key
    
    Store the private key with read and write permission for the user only
    and not with read permissions for everyone. This converts the
    write_file() function from fopen() to open() because open allows to
    specify the permission mask of the newly created file. It also adds and
    fixes some existing error handling.
    
    OpenSSL does this in the same way already.
    
    With this change it looks like this:
    root at OpenWrt:/# ls -al /etc/uhttpd.crt /etc/uhttpd.key
    -rw-r--r--    1 root     root           519 Nov  6 22:58 /etc/uhttpd.crt
    -rw-------    1 root     root           121 Nov  6 22:58 /etc/uhttpd.key
    
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
---
 package/utils/px5g-mbedtls/Makefile       |  2 +-
 package/utils/px5g-mbedtls/px5g-mbedtls.c | 35 +++++++++++++++++++++++--------
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/package/utils/px5g-mbedtls/Makefile b/package/utils/px5g-mbedtls/Makefile
index 6de5e55d06..14c9f684a9 100644
--- a/package/utils/px5g-mbedtls/Makefile
+++ b/package/utils/px5g-mbedtls/Makefile
@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=px5g-mbedtls
-PKG_RELEASE:=9
+PKG_RELEASE:=10
 PKG_LICENSE:=LGPL-2.1
 
 PKG_BUILD_FLAGS:=no-mips16
diff --git a/package/utils/px5g-mbedtls/px5g-mbedtls.c b/package/utils/px5g-mbedtls/px5g-mbedtls.c
index 4e0a73ab0a..85abe7dc73 100644
--- a/package/utils/px5g-mbedtls/px5g-mbedtls.c
+++ b/package/utils/px5g-mbedtls/px5g-mbedtls.c
@@ -30,6 +30,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <stdbool.h>
+#include <errno.h>
 
 #include <mbedtls/bignum.h>
 #include <mbedtls/entropy.h>
@@ -55,10 +56,13 @@ static int _urandom(void *ctx, unsigned char *out, size_t len)
 	return 0;
 }
 
-static void write_file(const char *path, int len, bool pem)
+static void write_file(const char *path, size_t len, bool pem, bool cert)
 {
-	FILE *f = stdout;
+	mode_t mode = S_IRUSR | S_IWUSR;
 	const char *buf_start = buf;
+	int fd = STDERR_FILENO;
+	ssize_t written;
+	int err;
 
 	if (!pem)
 		buf_start += sizeof(buf) - len;
@@ -67,17 +71,30 @@ static void write_file(const char *path, int len, bool pem)
 		fprintf(stderr, "No data to write\n");
 		exit(1);
 	}
+	
+	if (cert)
+		mode |= S_IRGRP | S_IROTH;
 
-	if (!f) {
+	if (path)
+		fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, mode);
+
+	if (fd < 0) {
 		fprintf(stderr, "error: I/O error\n");
 		exit(1);
 	}
 
+	written = write(fd, buf_start, len);
+	if (written != len) {
+		fprintf(stderr, "writing key failed with: %s\n", strerror(errno));
+		exit(1);
+	}
+	err = fsync(fd);
+	if (err < 0) {
+		fprintf(stderr, "syncing key failed with: %s\n", strerror(errno));
+		exit(1);
+	}
 	if (path)
-		f = fopen(path, "w");
-
-	fwrite(buf_start, 1, len, f);
-	fclose(f);
+		close(fd);
 }
 
 static mbedtls_ecp_group_id ecp_curve(const char *name)
@@ -110,7 +127,7 @@ static void write_key(mbedtls_pk_context *key, const char *path, bool pem)
 			len = 0;
 	}
 
-	write_file(path, len, pem);
+	write_file(path, len, pem, false);
 }
 
 static void gen_key(mbedtls_pk_context *key, bool rsa, int ksize, int exp,
@@ -301,7 +318,7 @@ int selfsigned(char **arg)
 			return 1;
 		}
 	}
-	write_file(certpath, len, pem);
+	write_file(certpath, len, pem, true);
 
 	mbedtls_x509write_crt_free(&cert);
 	mbedtls_mpi_free(&serial);